Project Summary (Kasus-Jacobi Project) Amyloid beta (A?) and the receptor for advanced glycation end-products (RAGE) are central to the pathogenesis of Alzheimer's disease (AD). No clinical intervention to stop or slow the progression of the disease is available, but a few clinical trials revealed encouraging results in terms of cognitive decline for patients with a mild form of the disease when A? or RAGE were targeted, demonstrating the validity of exploiting these targets for AD treatment. We have recently discovered that CAP37, a cationic antimicrobial protein, is significantly up regulated in the brains of patients with AD, binds and cleaves A?, and interacts with RAGE, which suggests that CAP37 modulates the pathogenesis of AD. Our long-term goal is to develop safe and effective therapeutic approaches targeting A?, RAGE and CAP37 for neurodegenerative diseases such as AD. Our objective in this application is to define the mechanistic and structural aspects of CAP37's interactions with RAGE and A?. The rationale for the proposed research is that a better understanding of how CAP37 regulates AD pathogenesis will guide the development of new drugs for the disease. We propose two specific aims. Our first aim is to define the CAP37-RAGE binding interface and determine how CAP37 interferes with the binding of other ligands of this receptor. Our working hypothesis for this aim is that CAP37 binds RAGE through a different domain than the other RAGE ligands. This may affect the binding of other ligands to RAGE through allosteric modification of the receptor. In this aim, we will elucidate the complex formed by CAP37 and RAGE. Successful completion of this aim will allow us to 1) propose a model for the binding of CAP37 to RAGE relative to A? and other RAGE ligands, 2) determine how the binding of CAP37 to RAGE interferes with the binding of other ligands, 3) propose a mechanism for a possible activation of RAGE by CAP37, and 4) if CAP37 activates RAGE, identify compounds with therapeutic potential for inhibition of endogenous CAP37 signaling through RAGE. Our second aim is to define the structural determinants of CAP37's binding and cleavage of A? and determine if CAP37 interferes with the polymerization of A?, which is the most relevant form of A? in AD. We will determine if CAP37 binds A? monomers and/or toxic polymers, and if the binding of CAP37 prevents or reverses the toxic polymerization of A?. We will define the mechanism by which CAP37, originally predicted to be enzymatically inactive, operates as a serine protease on A?, and determine if CAP37 can cleave polymerized A?. When our aims are accomplished, we will know the mechanisms by which CAP37 interferes with the A?-RAGE axis, leading to a better appreciation of how CAP37 might influence the progression of AD. This will allow the development of better therapeutics for AD and other neurodegenerative diseases involving A? and RAGE.